The Importance of DTP Codes and Brake Testing

Ensuring the roadworthiness of commercial vehicles is a cornerstone of safe and compliant fleet operation. As we continue to evolve our standards and practices, two areas of brake assessment demand particular attention: the correct use of DTP Codes and the technical execution of brake testing.

The Role and Importance of DTP Codes

DTP Codes, issued by the Driver and Vehicle Standards Agency (DVSA), are unique identifiers assigned to vehicle types during the type approval process. These codes are critical for:

• Identifying vehicle specifications: They link to detailed technical data, including axle weights, braking systems, and suspension types.

• Ensuring correct test parameters: When conducting brake tests, referencing the correct DTP Code ensures that the vehicle is tested against the appropriate performance benchmarks.

• Maintaining compliance: Using the wrong DTP Code can lead to inaccurate test results, potentially masking safety issues or leading to unnecessary failures.

Why Matching the Plating Details Matters

Each vehicle’s plating certificate includes the DTP Code, which must correspond exactly with the code used during brake testing. This alignment is essential because:

• Brake performance thresholds are DTP-specific: The DTP Code determines the minimum brake force values required for a pass. A mismatch could result in applying incorrect standards.

• Axle configurations and weights vary: Even small differences in axle spacing or suspension type can significantly affect braking dynamics. The DTP Code ensures the test reflects the actual vehicle setup.

• Legal and audit implications: Inaccurate DTP usage can invalidate test results and expose operators to compliance risks during inspections or audits.

Operators must regularly verify that the DTP Code on the vehicle’s plating certificate matches the one entered into the brake testing equipment. Any modifications to the vehicle, such as axle changes or suspension upgrades, must be reported, and the plating details should be updated accordingly.

Spotting an incorrect DTP Code:

Some examples of incorrect DTP codes are explained below,

• Axle showing ‘insufficient load’ - Operator calculated the load to be within the 65% requirement. DTP code was incorrect and axle 2 was assigned as 11500kg, which should have been 8500kg.

• Vehicle showing overloaded on axle weights – The Gross Vehicle Weight was incorrect at 18000kg, on a 26000kg vehicle

• Maintenance provider using old DPT code from PMI data – The vehicle had been issued with a new plating certificate after a notifiable alteration.

This is not an exhaustive list, as small differences in technical data can result in incorrect results.

Cross-Checking DTP Codes with DVSA Data

To support accuracy and transparency, the DVSA provides a publicly accessible Heavy Vehicle Brake Code (DTP Number) Database. This resource allows operators, testers, and engineers to:

• Verify DTP Codes against vehicle specifications

• Check axle weights, design gross vehicle weights, and braking configurations

• Ensure the correct DTP Code is used during brake testing

The database is available in spreadsheet format and can be downloaded from the UK Government’s data portal:
Heavy Vehicle Brake Code (DTP Number) Database – data.gov.uk

It is recommended that Authorised Testing Facilities (ATFs) and fleet operators keep a current version of this database installed on their brake testing systems to ensure new vehicle types are recognised and tested correctly.

Brake Testing: Technical Overview and Best Practice

Brake testing is not just a regulatory requirement—it’s a vital safety measure. The updated Guide to Maintaining Roadworthiness (effective April 2025) reinforces the expectation that every safety inspection includes a brake performance assessment.

Laden Roller Brake Testing

The most accurate method remains the laden roller brake test, which simulates real-world braking conditions by applying load to the vehicle.

Electronic Brake Performance Monitoring Systems (EBPMS)

Operators may choose to use an EBPMS system. EBPMS is deemed a viable alternative for trailer assessments. These systems continuously monitor braking performance during normal operations. However, they are not a shortcut:

• Data sufficiency: EBPMS must collect and store enough data to provide a reliable performance profile.

• Parking Brake. As EBPMS does not assess parking brake performance, DVSA expects that tug tests will be performed and recorded as part of the inspection process, or within the 14 days prior.

• Documentation: All findings must be recorded and reviewed regularly, by a competent person, to identify trends or emerging issues.

Decelerometer Testing

In certain cases, a decelerometer test may be used, particularly for vehicles that cannot be tested on a roller brake tester. This method measures the vehicle’s deceleration during a controlled stop and must include individual brake temperature readings to ensure accuracy. Decelerometer testing is not applicable for trailers.

Final Thoughts

Brake testing is a technical discipline that requires precision, understanding, and a commitment to safety. Whether using traditional roller brake testers or modern EBPMS solutions, operators must ensure that all tests are conducted competently and in line with the latest guidance.

DTP Codes must be correct and consistent with the vehicle’s plating details. This small but vital step ensures that brake testing is meaningful, compliant, and ultimately, safe.

At the RHA, we continue to support operators with training, accreditation, and technical advice to help them meet these evolving standards. For more information, visit our Roller Road Brake Testing Accreditation page.